Wood-derived resins, which are compatible with a variety of film-forming resins, and yet are substantially insoluble in some commonly used solvents such as aliphatic hydrocarbons, have found use in the formulation of coatings and plastics resistant to such materials. Such resins have also been utilized in adhesives, emulsions, cements, electrical insulation impregnants, inks, coating and bonding materials, and plastics. Use, however, in the rubber field has been limited to general purpose rubber compounding and rubber reclaiming. Thermoplastic resins obtained from wood have not been used in rubber stocks, nor, more specifically, as replacements for petroleum-derived process oils and/or resins, which are utilized in rubber stocks. Certain naturally occurring rosin-derived resins have been reportedly added to rubber tread stocks to compensate for the effect of carbon black therein; see U.S. Pat. No. 4,252,171 to Imai, et al.